Definition
An altitude or flight level maintained during en route level flight. It is a constant altitude assigned by ATC or selected by the pilot in compliance with the applicable flight rules.
Plain English
The steady altitude an aircraft holds during the main, level part of a flight — after the climb and before the descent.
Context Anchor
You will see this term in flight planning, air traffic control instructions, and discussions of altitude selection during the en route part of a flight.
Derivation
From 'cruise,' originally a sailing term meaning to sail steadily without a fixed destination in mind. In aviation it kept the sense of steady, level travel — the part of the flight between climbing out and descending in.
Why Pilots Care
Choosing the correct cruising altitude keeps the aircraft clear of traffic, improves fuel efficiency, and satisfies regulatory separation requirements.
Intuition Check
Cruising altitude does not mean any comfortable height the pilot happens to choose. It means a specific height selected, assigned, and maintained for the en route part of the flight.
Example Sentence 1
After leveling off, the pilot reported reaching her cruising altitude of 7,500 feet.
Example Sentence 2
After takeoff, ATC assigned a cruising altitude of 10,000 feet for the remainder of the IFR flight.